JP2001041269A - Electric brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speedily close up pad clearance and to improve responsiveness by forming a tilting surface of a ball ramp mechanism continuously from a plurality of tilting portions with various tilting angles. SOLUTION: When a rotor 11 rotates, linear movement of the rotor 11 is transmitted to a piston 13 through a thrust bearing 16, and the piston 13 moved left to activate a brake. At this time, an operation of a ball ramp mechanism 18 linearly moves the rotor 11 with rotation. The piston 13 rapidly displaces with the movement of a ball 17. Thus, because tilting angle is large when the ball 17 moves on a tilting portion 19a, less rotation amount of the rotor 11 can provide more displacement amount, the ball 17 extremely speedily passes through a pad clearance, and brake pads 7, 7 come into contact with a disk rotor 8 in a tilting portion 19b following the tilting portion 19a to perform braking.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric brake, and more particularly, to a mechanism capable of performing a linear motion while rotating a rotor portion of an electric motor as an actuator, wherein the mechanism is directly driven by the linear motion of the rotor. The present invention relates to a lightweight and small electric brake capable of operating a brake piston.

2. Description of the Related Art Conventionally, electric brakes are disclosed in
As disclosed in Japanese Patent No. 64351, a rotor that is rotated by energizing a stator is supported so as to be rotatable and movable in an axial direction, and a ball ramp mechanism is disposed between the rotor and a fixed member. By rotation
The rotor is linearly moved in the axial direction via the ball ramp mechanism, and the piston is operated by moving the rotor in the axial direction.

By the way, the power consumption or energy consumption of the electric brake when the brake braking occurs is determined uniquely according to the disk rotor rotation angle, so that the frequency of the brake operation is high and the braking force is high. However, there is a drawback that power consumption or energy consumption becomes large in a small area, and power consumption becomes large in a area having a large braking force. Despite these disadvantages, the ball ramp mechanism used in the prior art has a constant inclination angle of the ball ramp mechanism, and the linear movement of the brake pad is simple. There is a problem that power consumption or energy consumption cannot be reduced because of linearity. Further, if the inclination angle of the ball ramp mechanism is constant, there is a problem that it takes time to reduce the pad clearance between the brake pad and the disk rotor, and the response is deteriorated.

According to a first aspect of the present invention, there is provided an electric brake for rotating a rotor by energizing an actuator to convert the rotation of the rotor into an axial movement. It has a ramp mechanism, and the inclined surface of the ball ramp mechanism is configured such that a plurality of inclined portions having different inclination angles are continuously formed, so that power consumption or energy consumption can be reduced.
The responsiveness can be improved by reducing the pad clearance between the brake pad and the disk rotor in a short time. Further, in the electric brake according to the present invention, the axial movement amount per unit angle in the pad clearance formed between the brake pad and the disk rotor is larger than the axial movement amount per unit angle in the other inclined portions. Since the inclined portion is configured so that a large displacement can be obtained with a small amount of rotor rotation, it is possible to quickly pass the pad clearance and contact the brake pad with the disk rotor as quickly as possible, and obtain quick brake braking. it can. Furthermore, in the electric brake according to the third aspect, the amount of axial movement per unit angle in the region where the brake pad exerts a small braking force on the disk rotor is smaller than the amount of axial movement per unit angle in the other inclined portions. Since the inclined portion is configured as described above, the total energy consumption (power consumption × total operating time) due to the braking in the region where the operation frequency is high, that is, the region where the total operating time of the braking is large, is reduced. Further, in the electric brake according to the fourth aspect, the amount of axial movement per unit angle in a region where the braking force of the brake pad on the disk rotor is large is smaller than the amount of axial movement per unit angle in the other inclined portions. Since the inclined portion is configured as described above, the electric motor of the electric brake can be made smaller by the amount of less operation frequency.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.
FIG. 2 is a partially enlarged view of the ball ramp mechanism 18, and FIG. 3 is a view showing a displacement amount of the ball ramp mechanism 18 with respect to a rotation amount of the rotor 11. In FIG. 1, 1 is a pedal force provided on a brake pedal, a stroke sensor, 2 is an electronic control unit, 3 is a speed sensor, 4 is a caliper, 5 is a housing formed on the caliper, and 6 is an actuator built in the housing. Electric motor. The electric brake constituted by these components detects that the driver has operated the brake pedal by the pedaling force and the stroke sensor 1, and the electronic control unit 2 activates the electric motor 6 to linearly move the rotor in the motor. (The details will be described later.) To move the piston in the figure, and the brake pads 7, 7 serving as a pair of friction elements
Are moved in the mutual directions to pinch the disk rotor 8 so that a braking force can be applied. The treading force and stroke sensor 1 may be a sensor capable of detecting either the treading force or the stroke. The electric motor 6 has a stator 10 including a coil 9 fixed in a bore 5 a formed in the housing 5, and a rotor 11 disposed in the stator 10. Stator
The width of the rotor 10 is formed to be slightly smaller than the width of the rotor 11 so as not to protrude from the rotor 11 when the rotor 11 makes a linear motion as described later. As shown, a first rotating shaft 11a and a second rotating shaft 11b are formed integrally with the rotor 11,
The rotating shaft 11a is rotatably and slidably fitted to the piston 13 via the bearing 12, and the second rotating shaft 11b is rotatably and slidably supported by the housing 5 via the bearing 14. I have. The piston 13 is slidably held in a bore 5 a formed in the housing 5. A return spring 15 is provided between the piston 13 and the rotor 11, and furthermore, the axial movement of the rotor 11 is applied to the piston 13. A thrust bearing 16 for transmission is arranged. Also, the rotor 11
Between the housing and the housing 5, as shown in FIG.
(The rotor 11 is not shown in FIG. 2), and a ball ramp mechanism 18 constituted by the housing 5 and a ball 17 sandwiched by the housing 5 is arranged. As will be described later, linear motion is performed while rotating. In addition,
The moving distance of the rotor 11 in the linear direction is determined by the ball ramp mechanism 18.
Of the ball 17 and the shape of the inclined surface 19 (the inclined surface 19 formed on the rotor 11 and the housing 5) of the ball 17 storage portion. Next, the ball ramp mechanism 18 will be described with reference to FIGS. 2 and 3. FIG.
FIG. 4 is a diagram illustrating a rotation amount and a displacement amount. The symbols in this figure correspond to those in FIG. FIG. 2 is for easy understanding.
The actual inclined surface 19 is considerably exaggerated, and the broken line in each figure is a conventional inclined surface. Further, since the ball ramp mechanism 18 is the same on the rotor 11 side and the housing 5 side, the ball ramp mechanism 18 on the housing 5 will be described, and the description of the ball ramp mechanism 18 on the rotor 11 will be omitted. The ball ramp mechanism 18 has one inclined surface 19 shown in FIG.
Three sets are provided at intervals of 20 degrees. Stoppers 20, 21 are formed on both sides of the inclined surface 19 so as to protrude from the housing 5,
The ball 17 moves between the stoppers 20 and 21. If the position when the ball 17 is in contact with the stopper 20 is R0, the symbol R1 is the position where the brake pads 7, 7 contact the disk rotor 8, that is, the position where the pad clearance δ becomes zero. Reference symbol RE denotes a position when the ball 17 is in contact with the stopper 21, that is, a position where the brake pads 7, 7 contact the disk rotor 8 to maximize the braking force. Here, the position R0
The inclination angle of the inclined portion 19a of the inclined surface 19 from the position R1 to the position R1 is large, that is, the amount of displacement in the axial direction per unit rotation amount of the rotor 11 is large, and the ball 17 (The pad clearance δ is reduced to zero as quickly as possible), and the inclined portion 19b that follows the inclined portion 19a is smaller than the inclined angle angle of the inclined portion 19a. This is a section in which the pads 7, 7 come into contact with the disk rotor 8 to perform brake braking. In FIGS. 2 and 3, a section indicated by reference numeral XX is a section where brake braking is frequently performed. The operation of the electric brake of the present embodiment having the above configuration will be described. When the stroke sensor 1 detects that the driver has depressed the brake pedal, the coil 9 of the electric motor 6 is driven by a signal from the electronic control unit 2.
, And the rotor 11 starts rotating. The current value I at this time is determined by the thrust of the piston 13 required for braking, the displacement R per one rotation of the rotor 11 due to the shape of the inclined surface 19 of the ball 17 housing portion of the ball ramp mechanism 18, and the ball ramp mechanism 18
I = F × R / (2π × E × T) (1) from the mechanical efficiency E and the torque constant T of the electric motor 6. When the rotor 11 rotates, the linear movement of the rotor 11 is moved through the thrust bearing 16 to the piston.
The piston 13 is moved to the left in the drawing to actuate the brake. At this time, the operation of the ball ramp mechanism 18 causes the rotor 11 to move in a linear direction while rotating. That is, when the rotor 11 rotates in FIG. 2, the ball 17 moves along the inclined surface 19, whereby the rotor 11 moves in the axial direction (linear direction) according to the rotation amount of the rotor 11.
3, the piston 13 is rapidly displaced from the position A to the position B as the ball 17 moves. This is the ball
When the 17 moves on the inclined portion 19a, the inclination angle is large, so that a large displacement can be obtained with a small amount of rotation of the rotor 11, and the ball 17 passes through the pad clearance δ as fast as possible, and The brake pads 7, 7 are brought into contact with the disk rotor 8 at the inclined portion 19b following the portion 19a, and braking is performed. In general, desired brake braking is performed near the position C in the section XX. When the brake pedal is released, the electric motor 6 rotates in the reverse direction, the piston 13 returns to the initial state by the action of the return spring 15 and the interference between the brake pads 7, 7 and the disk rotor 8, and the braking force is released. Since the amount of movement of the piston 13 in the linear direction at the time of braking is determined by the amount of rotation of the rotor 11, the electronic control unit 2 uses the amount of rotation of the rotor 11 based on the pedaling force, the stroke sensor 1, or an input signal from the speed sensor. Is minutely controlled. Figures 4 and 5
This shows another embodiment of the present invention, in which the inclination angle in the region where the operation frequency is high is small on the inclined surface 29 of the ball 17 housing portion of the ball ramp mechanism 18, The same components as those described above are denoted by the same reference numerals, and different portions will be described. Also, in the present embodiment, the shape of the inclined surface 29 of the ball 17 housing portion of the ball ramp mechanism 18 is changed, and there is no change other than the inclined surface 29. Therefore, in the present embodiment, an enlarged view of the inclined surface 29,
Only a diagram showing the amount of rotation of the rotor 11 and the amount of displacement is shown. As described above, the shape of the inclined surface 29 is considerably exaggerated compared to the actual inclined surface 29 for easy understanding. 4 and 5, the ball 17 is a stopper.
Move between 20, 21. And the ball 17 is a stopper
If the position in contact with 20 is R0, the symbol R1
Is a position at which the brake pads 7, 7 contact the disk rotor 8, that is, a position at which the pad clearance δ becomes zero. Reference symbol R2 denotes frequent brake braking when the brake pads 7, 7 contact the disk rotor 8. The symbol RE is a position when the ball 17 is in contact with the stopper 21, that is, a position where the maximum brake braking is performed. Here, the inclined portion 29a of the inclined surface 29 from the position R0 to the position R1 has an intermediate inclination angle (compared to FIG. 2), and the ball 17 is moved to the pad clearance δ.
2 is made to pass quickly, if not as much as in FIG. 2. The slope 29b following the slope 29a is smaller than the slope angle of the slope 29a, and the brake pads 7, 7 are disc rotors. 8 is a section XX where brake braking is frequently performed in contact with No. 8. Note that this section XX
Is determined by experiment. The inclined portion 29c following the inclined portion 29b is larger than the inclined angle of the inclined portion 29b, and this section is a section where the brake braking is not frequently performed but a large brake braking is obtained. With the above configuration, in the shape of the inclined surface 29 of the ball 17 housing portion of the ball ramp mechanism 18 shown in FIG. 4, the inclination in the region XX where the operation frequency is high, that is, the region where the total operation time of braking is large, Since the size of the portion 29b is reduced, the value of the current flowing through the electric motor 6 is reduced according to the expression (1), and the total energy consumption (power consumption × total operating time) due to braking is reduced. In FIG. 5, the piston 13 is rapidly displaced from the position A to the position B as the ball 17 moves. This is because when the ball 17 moves on the inclined portion 19a, the inclination angle is large, so that a large displacement amount can be obtained with a small amount of rotation of the rotor 11, and the ball 17 has the pad clearance δ.
Pass as fast as possible. Since the brake braking is frequently performed from the position B to the position C, the amount of displacement with respect to the amount of rotation is reduced so that fine brake braking is performed. Piston again after position C
13 is a section where the ball 17 is suddenly displaced with the movement of the ball 17.
FIGS. 6 and 7 show still another embodiment of the present invention, in which the inclined surface 39 of the ball 17 accommodating portion of the ball ramp mechanism 18 has a smaller inclination angle in a region where the braking force is large. The same components as those of the above embodiment are denoted by the same reference numerals, and different portions will be described.
Further, in the present embodiment, the shape of the inclined surface 39 of the ball 17 housing portion of the ball ramp mechanism 18 is changed, and there is no change other than the inclined surface 39. Therefore, in the present embodiment, the inclined surface
Only an enlarged view of 39 and a view showing the rotation amount and the displacement amount of the rotor 11 are shown. As described above, the shape of the inclined surface 39 is considerably exaggerated than the actual inclined surface 39 for easy understanding. 6 and 7, the ball 17 moves between the stoppers 20 and 21. If the position where the ball 17 is in contact with the stopper 20 is R0, the symbol R3 is the position where the brake pads 7, 7 and the disk rotor 8 come into contact with a large force, that is, the maximum brake braking force. (The piston displacement at this time is represented by D). Here, from position R0 to position R3
The inclined portion 39a of the inclined surface 39 has an intermediate inclination angle (compared with FIG. 2), and the inclined portion 39a follows the inclined portion 39a.
39d is smaller than the inclination angle of the inclined portion 39a,
This is an area where the braking force is large. And this section YY is obtained by an experiment. FIG. 6 also shows a section XX in which the above-described brake braking is frequently performed. With the above configuration, in the present embodiment, the axial movement amount per unit angle in the area Y-Y where the brake pads 7, 7 apply a large brake braking force to the disk rotor 8 per unit angle in the other inclined portion 39a. Since the inclined portion 39d is configured to be smaller than the axial movement amount of the electric brake, the electric motor 11 of the electric brake
Can be reduced. Next, various modifications will be described. Each of the above embodiments has been described with reference to the case where the present invention is applied to the electric brake disclosed in Japanese Patent Application Laid-Open No. 9-264351, but the present invention is not limited to the application to the electric brake disclosed in Japanese Patent Application Laid-Open No. 9-264351. The invention may be applied to a ball ramp mechanism of an electric brake described in Japanese Patent Application No. 10-341055, and the present invention is applicable to any type of electric brake using a ball ramp mechanism. is there. Furthermore, in the above-described embodiment, all the inclined surfaces are constituted by straight lines. However, these inclined surfaces need not be straight lines, and may be curved lines approximating these straight lines. Are defined as having a large number of inclined portions.
Furthermore, when a curve is used for the inclined surface, a parabola, hyperbola,
Various curves such as cycloids may be used. Further, for example, in FIG. 5, the inclined portion 29a is formed of a straight line, the inclined portion 29b is formed of a parabola, and the inclined portion 29c is formed.
The inclined surface may be constituted by a straight line and a curved line such that the inclined surface is composed of a cycloid.

As described in detail above, the present invention has a ball ramp mechanism for rotating a rotor by energizing an actuator and converting the rotation of the rotor into axial movement. The inclined surface of the mechanism is configured such that a plurality of inclined portions having different inclination angles are continuously formed, and the amount of piston displacement with respect to the amount of rotor rotation can be arbitrarily set. Energy consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram of an electric brake according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of a ball ramp mechanism 18 of the electric brake according to one embodiment of the present invention.

3 is a diagram showing a displacement amount with respect to a rotor rotation amount of a ball ramp mechanism corresponding to FIG. 2;

FIG. 4 is a partially enlarged view of a ball ramp mechanism 18 of an electric brake according to another embodiment of the present invention.

FIG. 5 is a diagram illustrating a displacement amount with respect to a rotor rotation amount of the ball ramp mechanism corresponding to FIG. 4;

FIG. 6 is a partially enlarged view of a ball ramp mechanism 18 of an electric brake according to still another embodiment of the present invention.

7 is a diagram showing a displacement amount with respect to a rotor rotation amount of the ball ramp mechanism corresponding to FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Depressing force and stroke sensor provided on brake pedal 2 Electronic control unit 3 Speed sensor 4 Caliper 5 Housing 5a Bore 6 Electric motor 7, 7 Brake pad 8 Disk rotor 9 Coil 10 Stator 11 Rotor 11a First rotating shaft 11b Second rotation Shaft 12 Bearing 13 Piston 14 Bearing 15 Return spring 16 Thrust bearing 17 Ball 18 Ball ramp mechanism 19 Inclined surface 20 Stopper 21 Stopper 19a Inclined portion 19b Inclined portion 29 Inclined portion 29a Inclined portion 29b Inclined portion 29c Inclined portion 39 Inclined surface 39a Inclined portion 39d Inclined part A, B, C, D position R0, R1, R2, R3, RE position δ Pad clearance XX section YY section

Claims (4)

[Claims] 1. An electric brake comprising a ball ramp mechanism for rotating a rotor by energizing an actuator and converting the rotation of the rotor into an axial movement, wherein the inclined surface of the ball ramp mechanism has an inclination angle. An electric brake, wherein a plurality of different inclined portions are continuously formed. 2. An inclined portion such that an axial movement amount per unit angle in a pad clearance formed between a brake pad and a disk rotor is larger than an axial movement amount per unit angle in another inclined portion. The electric brake according to claim 1, wherein the electric brake is configured. 3. An inclined portion such that an axial movement amount per unit angle in a region where brake braking force of a brake pad to a disk rotor is small is smaller than an axial movement amount per unit angle in another inclined portion. The electric brake according to claim 1, wherein the electric brake is configured. 4. An inclined portion such that an axial movement amount per unit angle in a region where a brake braking force applied to a disk rotor by a brake pad is large is smaller than an axial movement amount per unit angle in another inclined portion. The electric brake according to claim 1, wherein the electric brake is configured.